The School Board imposed new salaries and working conditions on 21,000 teachers in the nation's fifth-largest school district after negotiators failed Thursday to reach a contract agreement.
The Philadelphia Board of Education unanimously approved the new work rules on the recommendation of Mayor John Street, who had set a deadline of 7 p.m. Thursday for a settlement.
The Philadelphia Federation of Teachers had threatened its first strike since 1981, potentially idling 210,000 students, if the city imposed the interim work rules. But union officials did not immediately call a walkout.
The union must give two days' notice of a strike, meaning that the earliest teachers could be out of school is Monday.
The new terms would extend the school day by one hour and the school year by two days, give principals more say over where teachers are assigned and implement a merit pay system. In exchange, the teachers would get a $500 bonus and a raise of 17 percent over five years.
The union said the terms would impose longer hours for teachers without enough of a pay increase.